# Green Function approach is more physical?

1. Jun 29, 2008

### robousy

Hey folks,

I'm not really sure which forum to put this question in but I figured this was probably the best as it deals with issues of regularization.

I'm reading Miltons 'The Casimir Effect'. In chapter one he derives the Casimir energy for a massless scalar field by employing dimensional regularization. He then goes on in the next section to derive the same result using a Green function approach which he claims is "...a physical and rigorous approach".

From this sentence it appears that he favors the Green function approach over Dim reg. Is this a general 'feeling' in the physics community? That Green functions are somehow superior to Dim Reg? Also, why should this be 'physical'?

I hope this question makes sense.

Rich

2. Jun 30, 2008

### CompuChip

I do have the feeling that Greens functions are more physical than dimensional regularization. That is, I can very well imagine the physical meaning of a propagator, but I don't really have intuition for $4 + \epsilon$ dimensions with $\epsilon \in \mathbb{C}$.
I can't remember seeing Greens functions being used for regularization though.